1、 Reference number ISO/TR 26762:2008(E) ISO 2008TECHNICAL REPORT ISO/TR 26762 First edition 2008-07-15 Natural gas Upstream area Allocation of gas and condensate Gaz naturel Zone amont Allocation du gaz et du condensat ISO/TR 26762:2008(E) PDF disclaimer This PDF file may contain embedded typefaces.
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6、ight office Case postale 56 CH-1211 Geneva 20 Tel. + 41 22 749 01 11 Fax + 41 22 749 09 47 E-mail copyrightiso.org Web www.iso.org Published in Switzerland ii ISO 2008 All rights reservedISO/TR 26762:2008(E) ISO 2008 All rights reserved iii Contents Page Foreword. v Introduction . vi 1 Scope 1 2 Nor
7、mative references 1 3 Economic aspects .1 3.1 Overview .1 3.2 Uncertainty and costs .3 3.3 Allocation system overview4 4 Allocation from different viewpoints and terminology 7 4.1 Physical system.7 4.2 Gas/condensate system overview .7 4.3 Physical system terms 12 4.4 Definitions for allocation syst
8、ems .14 4.5 Allocation from a commercial viewpoint.16 5 Quantity measurement for gas and condensate 21 5.1 Introduction21 5.2 Quantity measurement by type of fluid streams 23 6 Quality measurement 33 6.1 Sampling and analysis 33 6.2 Analysis 35 6.3 Uncertainties 35 6.4 Other .36 7 Data processing.38
9、 7.1 Calculation at the measurement point.38 7.2 Balancing and reconciliation39 7.3 Process simulation40 7.4 Line packing and stock change .41 8 Lift, injection and utility gas .42 8.1 General42 8.2 Lift gas 42 8.3 Injection gas .43 8.4 Utility gas43 8.5 Uncertainty considerations for lift, injectio
10、n and utility gas.44 9 Uncertainty General considerations .45 9.1 Economic consequences45 9.2 Sensitivity.47 9.3 Allocation principle48 9.4 Uncertainty determination 48 10 Validation49 10.1 General49 10.2 Meter validation49 10.3 Allocation procedures and process validation.50 10.4 Data validation .5
11、0 10.5 Process-model validation .50 10.6 Allocation-process results validation50 10.7 Software validation50 ISO/TR 26762:2008(E) iv ISO 2008 All rights reserved11 Classification of allocation processes 51 11.1 General descriptions and calculations . 51 11.2 Allocation systems layout 60 12 Mis-measur
12、ements Measurement-correction and estimations . 65 Annex A (informative) Adjust for impurities 66 Annex B (informative) Adjustments for fuel/utility/vent/flare gas . 67 Annex C (informative) Wet gas 68 Annex D (informative) Codes, abbreviations and acronyms . 71 Annex E (informative) Conversion of m
13、olar percent to mass percent 73 Annex F (informative) Conversion of mole percent to per cent of the calorific value. 74 Annex G (informative) Conversion of mole per cent to volume percent 75 Annex H (informative) Components of gas and liquid reported 76 Bibliography . 77 ISO/TR 26762:2008(E) ISO 200
14、8 All rights reserved v Foreword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical committees. Each member body interested in
15、 a subject for which a technical committee has been established has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commiss
16、ion (IEC) on all matters of electrotechnical standardization. International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2. The main task of technical committees is to prepare International Standards. Draft International Standards adopted by the technical
17、committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote. In exceptional circumstances, when a technical committee has collected data of a different kind from that which is normally publ
18、ished as an International Standard (“state of the art”, for example), it may decide by a simple majority vote of its participating members to publish a Technical Report. A Technical Report is entirely informative in nature and does not have to be reviewed until the data it provides are considered to
19、 be no longer valid or useful. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. ISO/TR 26762 was prepared by Technical Committee ISO/TC 193, Natural g
20、as. ISO/TR 26762:2008(E) vi ISO 2008 All rights reservedIntroduction Hydrocarbon gas and condensate from onshore or offshore concessions is often transported by shared pipelines to shared main treatment facilities. The concessions are often owned by or licensed to a number of oil companies. At the m
21、ain treatment facilities, the gas and condensate are processed to sales specifications. The gas is sold to shippers in terms of standard volume (standard cubic metres) or combustion energy (joules), and the condensate is sold in terms of standard volume (standard cubic metres) or mass (kilograms or
22、tonnes). All the gas and condensate sold at the main treatment facility and the associated money should be allocated back to the individual concessions and, ultimately, to the individual reservoirs or wells, as illustrated in Figure 1. When gas from two or more entry sources (e.g. two or more differ
23、ent companies) is commingled and processed in a common pipeline and terminal system and the sources have different ownership and/or operate under different tax regimes, then a gas allocation system is required. It is necessary that the allocation system provide a fair, equitable and auditable means
24、of sharing out the products from the system to the entry sources and to the associated partners, recognizing the specific delivery requirements of each participant. Figure 1 Offshore gas distributions TECHNICAL REPORT ISO/TR 26762:2008(E) ISO 2008 All rights reserved 1 Natural gas Upstream area Allo
25、cation of gas and condensate 1 Scope This Technical Report describes the production measurements, in terms of both hardware and procedures, that can be used to allocate the gas and condensate back to the individual concessions, reservoirs and wells in a fair and equitable way. The objective is to gi
26、ve an approach that is recognized to be current best practice and that has a wide support in the oil and gas industry. 2 Normative references ISO 5167-1, Measurement of fluid flow by means of pressure differential devices inserted in circular cross- section conduits running full Part 1: General prin
27、ciples and requirements ISO 5168, Measurement of fluid flow Procedures for the evaluation of uncertainties ISO 6974 (all parts), Natural gas Determination of composition with defined uncertainty by gas chromatography ISO 6975, Natural gas Extended analysis Gas-chromatographic method ISO 6976:1995, N
28、atural gas Calculation of calorific values, density, relative density and Wobbe index from composition ISO 9951, Measurement of gas flow in closed conduits Turbine meters ISO 10715, Natural gas Sampling guidelines 3 Economic aspects 3.1 Overview 3.1.1 General Production measurements in the upstream
29、area, whether single-phase or multiphase, have an economic impact on the business. The implementation of production measurements costs money, but in return delivers data that can be used in decision-making processes and in measuring the economic returns. Generally, it is necessary to give the three
30、issues described in 3.1.2 to 3.1.4 proper consideration to implement a cost- effective measurement and allocation system. ISO/TR 26762:2008(E) 2 ISO 2008 All rights reserved3.1.2 Value of information The decision-making processes that use production measurement information are those associated with
31、production optimization or reservoir modelling. Figure 2 indicates, schematically, the effect of measurement accuracy on the uncertainty band of the ultimate recovery from a concession (i.e. total production over field life). With poor accuracy in the measurements, the uncertainty band and associate
32、d risk exposure stay relatively large. With better and more accurate measurements, the uncertainty band and associated financial risk are reduced. The assessment of the value of information is the most difficult part of designing an allocation system and it is probably for that reason that it is rar
33、ely done properly, if at all. As an example, the difference between production allocation (i.e. allocation of fluids from a production facility to the individual wells) and sales allocation (i.e. allocation of products in a common pipeline) can be mentioned. In the sales allocation, it can be direct
34、ly calculated what the relation is between uncertainties in fluid flow measurement and risk in money flow between the companies involved. In the production allocation, often within one single company, this is less obvious as complex reservoir modelling and petroleum economics are involved. This is o
35、ften why, in general, the requirements for sales allocation are higher than the requirements for production allocation. 3.1.3 Hardware costs Capital expenditures for production facilities, test separators, test lines, multiphase flow meters, etc. can all be assessed relatively easily. It should also
36、 be noted that the higher the accuracy requirement for a particular meter, the more expensive the meter hardware. This is the easiest part in the total cost estimate. Figure 2 Cost treatment of metering ISO/TR 26762:2008(E) ISO 2008 All rights reserved 3 3.1.4 Operating costs Preparation and impleme
37、ntation of procedures and guidelines to keep the production measurement equipment in good shape (maintenance, verification and calibration) and to ensure that readings are reliable and within the original specifications require sufficient and consistent dedication during the operations phase. These
38、costs are often underestimated, especially with new technologies such as multiphase or wet-gas flow metering. 3.2 Uncertainty and costs With respect to uncertainty and costs, two extreme cases are considered. One extreme is a production system with very high accuracy in production measurements. Due
39、to increased hardware costs and intensive operator involvement, the project and operating costs are higher, but with more and better information, better reservoir management and production optimization can be carried out. Consequently, the uncertainty band in the ultimate recovery decreases, giving
40、a lower spread in project and operating risks (see Figure 2). Realizing that the value of the oil in the ground is limited, we can also conclude that at a certain cost level the development becomes economically unattractive. The other extreme is a poor accuracy in the production measurements or prod
41、uction is not measured at all. Poor reservoir management, sub-optimal production optimization and potential loss of revenue are the result. Consequently, the uncertainty band in the ultimate recovery stays large. The development can unwittingly become unattractive from an economic and risk point of
42、view. Somewhere between the above two extremes there is an optimum acceptable uncertainty, with the associated costs for the measurement and allocation processes. This is illustrated in Figure 3, in which costs (in arbitrary units) are plotted against acceptable uncertainty. This optimum can well be
43、 different for each individual hydrocarbon development. It can well be the case that, for a particular development, an accuracy of 10 % in gas flow rate is sufficient while in another development a 2 % accuracy is required. Figure 3 Costs related to uncertainty ISO/TR 26762:2008(E) 4 ISO 2008 All ri
44、ghts reserved3.3 Allocation system overview It is not unusual to take between one and two years to negotiate all the terms of a gas and condensate allocation agreement. A wide array of skills is required to understand the diverse topics in the development of an allocation system. To successfully con
45、clude an agreement, it is good practice to form a team with expertise in the following: commercial negotiation; gas legislation; gas marketing; measurement and allocation; production operation; IT. Besides the preparation of the commercial agreement, it is necessary to develop the business processes
46、 to manage the day-to-day operation of the agreement. It is imperative to establish responsibilities and ownership for the following: hydrocarbon stream meter data; hydrocarbon stream analysis; production forecast information; allocation system operation. Development of the business processes requir
47、es a review of almost all departments within a gas production organization to ensure that the workload associated with the operation of the allocation system can be performed adequately and to identify whether additional personnel or external resources are required. 3.3.1 Overall scope of an allocat
48、ion agreement Figure 4 gives an overview of the major issues that feature in a gas and condensate allocation agreement. These issues are discussed separately in the following subclauses. One party or department should be charged with overall responsibility for producing the agreement, but the party
49、or department may vary from company to company. It is of utmost importance that all parties or departments involved in the agreement ensure that the issues affecting them are properly and adequately dealt with in the agreement. 3.3.2 Reservoir performance Reservoir performance data are required to assist in the forecasting of production to the operator of the gas treatment facilities. Long-term forecasts issued are likely based partly on the technical view of the reservoir potential and p
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